why furnaces stop working

Top Reasons Why Furnaces Stop Working

Winter is here, meaning staying warm is of the utmost importance. A furnace that works efficiently and effectively is the key to ensuring that your home is a warm haven during the cold months. There’s nothing worse than coming home to a house that’s as cold as the outdoors, usually caused by a malfunctioning furnace.

The frustration can be overwhelming and can cause a great deal of inconvenience to home dwellers. Hence, knowing why furnaces stop working is crucial to prevent such situations.

In this guide, we will provide you with an overview of the top reasons why furnaces stop working. We will also discuss the importance of furnaces during winter and why ensuring they are working seamlessly is crucial.

Lack of Maintenance

Regular maintenance is essential to keep your furnace in top condition. It helps in identifying potential problems before they cause major breakdowns. During regular maintenance, professional technicians can detect and fix small issues before they escalate into major problems. It can result in significant savings in repair costs and can add life to your unit.

Regular maintenance also helps to keep your furnace running efficiently. A well-maintained furnace uses less energy, reduces your energy bills, and has less impact on the environment. It will also improve the indoor air quality of your home by reducing the amount of dust, debris, and pollutants in the air.

Simple Maintenance Tasks that Can Prevent Furnace Breakdowns

While some maintenance tasks require a professional technician, there are simple things you can do yourself to keep your furnace running efficiently. Here are some examples:

  • Replace Air Filters – Dirty air filters can cause furnace breakdowns. Replace them once a month during the winter season. Clean filters can help to improve airflow, reduce energy bills, and prolong the life of your furnace.
  • Clean the Unit – Clean the furnace regularly to remove any debris, dust, and dirt that may have accumulated on and around the unit. It can prevent overheating and improve operational efficiency.
  • Schedule Annual Professional Inspection – Always schedule an annual furnace inspection by a professional technician to ensure everything works smoothly.
  • Check the Thermostat – Ensure that your thermostat is working correctly. If not, replace it with a newer, more reliable model. A malfunctioning thermostat can cause your furnace to run constantly, depending on the thermostat’s issue.

Thermostat Malfunction

A thermostat is a device that regulates your home’s temperature, ensuring it remains at your desired temperature. It detects the temperature in your home and signals the furnace to turn on or off to keep the temperature constant. It also enables you to adjust and control the temperature with ease.

Symptoms of a Malfunctioning Thermostat

A malfunctioning thermostat can cause a lot of frustration and inconvenience by affecting the temperature inside your home. Here are some signs that could indicate a malfunctioning thermostat:

  • Inaccurate Temperature Control – If you set your thermostat at a certain temperature and your furnace doesn’t respond, your thermostat might malfunction.
  • Constant Running – A faulty thermostat might cause your furnace to run constantly, even if the desired temperature has been reached.
  • Short Cycling – A malfunctioning thermostat may cause your furnace to continually turn on and off, which can cause unnecessary wear and tear on your unit.
  • No Heat – If your furnace doesn’t produce heat or turn on, it could be due to a malfunctioning thermostat.

Importance of Replacing a Malfunctioning Thermostat

If you suspect your thermostat is malfunctioning, replacing it as soon as possible is essential. A malfunctioning thermostat can cause your furnace to run inefficiently, leading to higher energy bills and wear and tear on your unit. Replacing your thermostat with a newer, more reliable model can help prevent these issues and ensure that your furnace is regulating the temperature in your home effectively.

Pilot Light or Ignition Control Issues

A pilot light is a small flame that ignites the gas in your furnace. The pilot light’s flame is a permanent light responsible for heating the thermocouple, which signals the valve to open, allowing gas to flow to the main burner.

Causes of Pilot Light Failure

Several factors, such as a blown-out pilot light or a faulty thermocouple, can cause pilot light failure. Here are some common causes:

  • Dirty Pilot Light – If the pilot light is dirty or clogged with debris, it may not function correctly.
  • Damaged Pilot Light – If the pilot light is damaged or worn out, it will not generate enough heat to open the gas valve.
  • Faulty Thermocouple – A faulty thermocouple can cause the pilot light to go out, preventing your furnace from igniting.

Overview of Ignition Control and Its Issues

Ignition control is responsible for managing the ignition sequence in your furnace. It starts by checking the thermostat setting and then initiates the ignition process by sending a signal to the gas valve. If the ignition control malfunctions, your furnace can fail to start or experience problems in the ignition sequence.

The issues with ignition control could result from several different factors. The most common causes of ignition control problems include faulty wiring, a malfunctioning fan limit switch, or a damaged control board.

Dirty or Clogged Air Filters

Air filters trap dust, debris, and other particles from circulating through your home’s air. These filters play a crucial role in maintaining your indoor air quality and improving the efficiency of your heating and cooling system. The filter captures these impurities and helps prevent damage to your furnace by protecting it from dirt and debris.

Symptoms of Dirty or Clogged Air Filters

Dirty or clogged air filters can cause a variety of problems, including:

  • Uneven Heating – If the air filter is clogged, it can restrict airflow, causing uneven heating in your home.
  • Dust Buildup – You might notice more dust and debris buildup in your home if you have dirty air filters.
  • Overheating – When air filters are filthy, they block airflow to the furnace, causing it to overheat and potentially shut down.
  • Higher Energy Bills – A clogged air filter makes your furnace work harder, increasing energy bills.

Mechanical Wear and Tear

Furnaces are complex machines with hundreds of parts. Over time, these components can wear out, become damaged, or break down due to normal use and everyday wear and tear. Neglecting regular maintenance can also contribute to more significant mechanical problems in the long run.

Types of Mechanical Failures

Mechanical failures may occur due to factors such as age and lack of maintenance. These are some common types of mechanical failures:

  • Blower Fan Failures – The blower fan is an essential component in your furnace that pulls air from your home through the filter system and distributes it throughout your home. If the blower fan is worn out or damaged, it can lead to inefficient heating in your home.
  • Ignition System Failures – The ignition system controls the gas flow to your furnace’s main burner and ignites it when necessary. If there is a problem with the ignition system or its components are worn out, it may cause your furnace to fail to ignite or have issues during ignition.
  • Loose Connections – Loose wiring connections can cause problems with various components within the furnace system, like switches and sensors, which may result in improper unit functioning.


Various factors, including dirty or clogged air filters, faulty wiring, damaged components, and mechanical wear and tear, can cause furnace problems. Regular maintenance is key to keeping your furnace in good working order. If you suspect that there may be an issue with your furnace, it’s best to contact a professional HVAC technician for assistance. They can diagnose the problem and help you find a solution to get your furnace back up and running quickly.